The high temperatures reached by parts of an automotive engine, especially by present day automobiles having catalytic converters, provides a good heat source for the generation of usable electrical or mechanical power by a heat engine. A heat engine used in extracting waste heat from an automobile engine, say the exhaust pipe area, offers high efficiency. One reason is that the engine performance will not be degraded since the heat extracted is waste heat which was not doing work. Efficiency is also increased because any power consuming accessories of the automobile are driven by the heat engine instead of normally being driven directly by the automobile engine or by engine-generated electricity. There are many methods of extracting waste heat from the automobile engine. Two examples are that heat can be removed from the exhaust manifold or may be extracted from the liquid cooling system by some heat exchange method.
A rough calculation of the amount of power that can be generated by the present heat engine is as follows. Assume that a 250 horsepower automobile engine is 50% efficient. This means that 500 horsepower must be generated by the burning fuel and that 250 horsepower goes into heat. Of that amount of heat, at least 80% goes out the exhaust. If 50% of that heat is delivered to a 25% efficient heat engine, the output of that heat engine would be work, W, of about EQU W = (250) (0.8) (0.5) (0.25) = 25 horsepower EQU W = 18,650 watts
A specific embodiment of the present invention uses a Stirling engine as the heat engine.